To brake a traveling vehicle to a slower speed or to a stop, a significant amount of energy must be dissipated. A large part of this energy is converted into heat that tends to raise the temperature of the brake rotor. In order to prevent brake overheating and to reduce brake wear which increases with higher temperatures, an adequate provision is typically made for transferring away the heat load generated in vehicle rotors. Often, brake rotors are assembled in applications where external surface heat transfer is sufficient and internal ventilation is not required. Other applications require ventilation air flow through the rotor itself.
Conventional ventilated brake rotors generally include a pair of mutually spaced-apart annular disks that present two opposed external surfaces for engaging brake pads under the clamping operation of a braking actuator. The space between the disks typically includes a number of vanes with flow passages defied between each pair of adjacent vanes that extend between the disks from their inner diameter to their outer diameter. Rotation of the rotor causes the vanes to induce air flow through the flow passages from the inner diameter to the outer diameter of the disks, providing increased convective heat transfer from the rotor.
It is known that brake rotor design plays an important role in brake cooling. U.S. Pat. No. 5,492,205 discloses a rotor utilizing a vane configuration that accommodates the rotor's air flow regime, includes an optimal vane number for a given rotor design resulting in high flow efficiency, and provides a flow passage profile that results in reduced flow restriction and improved cooling air flow. That patent describes a rotor with a straight vane profile.
A brake rotor is generally designed for use within a particular application where surrounding structures impact the rotor's size. Constraints exist on the outer and inner diameters of the rotor's air flow area, and on the total rotor thickness between braking surfaces. Additionally, manufacturing requirements limit the amount that the cross sectional area of the rotor structure can vary. Therefore, the convective heat transfer surface area of the rotor is limited by design constraints that are imposed by the application into which the rotor is integrated.
The vent section of the rotor however, does allow for design flexibility. The vent section, particularly the vane surface, affects the heat transfer rate. Proper design of the vent section can have a favorable impact on the rotor's overall cooling performance. It is generally believed that a curved vane profile is inherently more efficient than a straight vane profile for cooling air flow purposes. However, the use of curved vanes is often undesirable because it entails the use of oppositely curved vanes on opposite sides of the vehicle leading to a proliferation of component part numbers. Therefore, a majority of ventilated brake rotors have straight vanes so that they are adaptable to use on both sides of a vehicle. Accordingly, the development of curved vane rotors has been intermittent, leading to a present need for an aerodynamically efficient design that achieves minimum incident and viscous losses. In order to provide an improved air flow rate for an increased brake rotor cooling effect, a brake rotor with an optimized curved vane configuration is sought that provides a low restriction air flow passage, in a configuration that is adapted to increase flow rate resulting in an enhanced heat transfer mechanism.